[Hallicrafters] Xmtr noise getting into Rcvr

[J. Steven Cochrane]

I recently recreated my first station, a Hallicrafters HT-46, SX-146, R-48 and an E. F. Johnson T/R Switch. The SX-146 and the HT-46 both work great except when I put them into transceive configuration and place the HT-46 Operation switch in the appropriate upper or lower sideband, then the SX-146 starts receiving a 20 db over nine noise, it sounds like white noise except on 20 meters were I actually get a tone.  As soon as I place the HT-46 Operation switch back in Stand-by the noise goes away and the receiver works great. 
1. The SX-146 Inject Cable to the HT-46 is 75 Ohm coax. 
2. I have synchronized the upper and lower sideband oscillators in the SX-146 with the HT-46.
3. I have received excellent audio reports on the air for the transmitter.
4. The receiver has great sensitivity and selectivity except when the transmitter Operation Switch is placed in the USB or LSB position.
5. I have shortened the coax from the HT-46 to the T/R switch as much as possible (the T/R switch directions address this as a possible source of noise in the receiver).

My thoughts are to start with troubleshooting the T/R Switch (the electrolytic capacitor has been replaced in it) and possibly adjusting the T/R switch (if there is any adjustments) which may be over amplifying any noise generated in the finals of the transmitter and allowing that to get into the receiver when in the receive mode.

Has anyone had this problem and know a cure, preferably a simple one?
Thanks,

Steve
J. Steven Cochrane, W7JSC